Sulfur amino acids play a role in the regulation of blood pressure through a mechanism that is uncertain at present. There is evidence that taurine plays a role in the release or activation of ANF. We tested the effects of acute bolus injections of sulfur amino acids on blood pressure, plasma atrial natriuretic peptide and hemodynamic parameters in SHR and WKR rats. We found that: in SHR, acute bolus injections of sulfur amino acids reduces the levels of blood pressure 20-30%, heart rate 10-15%, total peripheral resistance 20-35%. Cardiac output remains unchanged, plasma ANF increases 3 fold. Administration of the same doses in pitched rats also reduces blood pressure 30-50%. In WKR we observed the same results at higher doses: 2 fold for taurine- cysteine sulfinic acid and 4 fold for methionine-penicillamine. We conclude that sulfur amino acids contribute to the regulation of blood pressure by a central mechanism (reduction of heart rate) and by a peripheral mechanism (reduction of total peripheral resistance).